Tar sand recovery method

ABSTRACT

Bitumen may be efficiently and economically extracted from tar sand deposits in situ by imbibition flooding. The imbibition flooding is performed in two general steps. First, the tar sand deposits are contacted with a bitumen solvent followed by a soak period to allow imbibition of the solvent. Next, the tar sands are contacted with an aqueous fluid followed by a soak period to allow imbibition. The freed bitumen is then produced by conventional means.

2 01.3 methane united States Patent [191 Carlin 1 May21,1974

Primary Examiner-David H. Brown Attorney, Agent, or FirmT. H. Whaley; C. G. Reis 5 7] ABSTRACT Bitumen may be efficiently and economically extracted from tar sand deposits in situ by imbibition flooding. The imbibition flooding is performed in two general steps. First, the tar sand deposits are contacted with a bitumen solvent followed by a soak period to allow imbibition of the solvent. Next, the tar sands are contacted with an aqueous fluid followed by a soak period to allow imbibition. The freed bitumen is then produced by conventional means.

10 Claims, 2 Drawing Figures 1 TAR SAND RECOVERY METHOD [75] Inventor: Joseph T. Carlin, Houston, Tex.

[73] Assignee: Texaco Inc., New York, NY.

[22] Filed: Feb. 12, 1973 [21] Appl. No.: 331,391

[52] US. Cl 166/274, 166/305 [51] Int. Cl E21b 43/22 [58] Field of Search 166/274, 271, 304, 305

[5 6] References Cited UNITED STATES PATENTS 2,365,591 12/1944 Ranney.. 166/274 X 2,792,894 5/1957 Graham et a1. 166/305 2,909,224 10/1959 Allen 166/305 2,998,066 8/1961 Nixon; 166/304 3,131,759 5/1964 Slusser et al 166/305 3,240,272 3/1966 Orkiszewski 166/274 PATENTEUMAY 21 1914 81 1; 5 06 TAR SAND RECOVERY METHOD BACKGROUND OF THE INVENTION 1. Field of the Invention This invention concerns the in situ recovery of bitu-, men from tar sands.

2. Description of the Prior Art A great volume of hydrocarbons exist in known deposits of tar sands. These deposits occur at various places, the Athabasca tar sands being an example.

Some tar sand formations are unconsolidated, i.e., the inorganic minerals or sands have no continuity and exist as mostly separated particles each surrounded completely by petroleum and water. Typically, in the unconsolidated formations, a grain of sand is surrounded by an envelope-of water and this water envelope is surrounded by a petroleum envelope. Other tar sand fonnations have a consolidated matrix of inorganic materials and may even be oil wet, i.e., the hydrocarbon wets the sand grain. The petroleum in a tar sand deposit is an asphaltic bitumen of a highly viscous nature ranging from a liquid to a semi-solid. Although there is no universally acceptable way of defining tar sand petroleum, these hydrocarbons are usually characterized by being very viscous or even non-flowable under reservoir conditions by the application of driving fluid pressure. Further, the reservoirs in which they occur generally lack any substantial sources of natural driving energy such as a natural water or gas drive.

Where surface mining is not feasible the petroleum must be recovered by rendering the tarry bitumen mobile in situ and producing it through a well penetrating the tar sand deposit. These in situ methods of bitumen recovery include thermal, both steam and in situ combustion, and solvent techniques. In situ combustion has not been very successful because the permeability of the tar sand is sharply reduced by the three phases of gas, water and oil ahead of the combustion front. Furthermore, the tar sand oil ahead of the combustion front remains cold and immobile. To overcome this, attempts have been made to create a permeable channel through the tar sand from an injection well to a production well, and thereafter injecting air into the channel. In theory, the oil in the formation would diffuse into the channel burn and thereby heat the oil in the tar sands to increase its mobility. However, success has not been apparent since in practice the air injected largely bypasses the oil in the formation, flows into the production well, and ignites oil in the production well. Thermal methods involving steam are not economical at present.

The use of solvent in situ by injecting the solvent and producing it back (push-pull) is not economical because of the high cost of solvent. An excessive amount of solvent is retained by the formation. The use of solvent slugs followed by water flood in a conventional through put operation is not economical because of viscosity differences and sweep efficiencies.

The method of my invention overcomes these difficulties. 1

SUMMARY OF THE INVENTION The invention is amethod for extracting bitumen in situ from tar sand deposits by contacting a tar sand deposit with .a bitumen solvent for a sufficient time to allow imbibition of the solvent into the tar sand followed by contacting the tar sand deposit with an aqueousfluid to allow imbibition of the aqueous fluid into the tar sand. The bitumen, solvent, and aqueous fluid are then produced.

BRIEF DESCRIPTION OF THE DRAWING The drawing depicts a typical embodiment of my imbibition recovery process in a tar sand.

DESCRIPTION OF THE PREFERRED EMBODIMENTS enough to be produced.

In a typical embodiment of my invention a solvent for the bitumen is injected into a well penetrating a tar sand deposit and is forced out into the formation to a desired radius. Injection is then stopped and the solvent is allowed to soak or imbibe into the tar sand deposit. By allowing this imbibition to take place the envelope of bitumen surrounding the sand particle is broken. In the next step, an aqueous fluid is introduced into the formation and is also allowed to imbibe into the tar sand deposit. Since the envelope of bitumen is broken, the aqueous fluid may more easily dislodge the bitumen from the sand particle or matrix. The final step is to produce the fluids: aqueous fluid, solvent, and bitumen by conventional means through the same well as injection took place.

Before the above procedure is begun the tar sand deposit may be made more receptive to the fluids to be injected by fracturing or other means known to the art.

In another typical embodiment of my invention at least two wells penetrate the tar sand. One is an injection well and one is a production well. The solvent is injected into the tar sand deposit through the injection well and is preferably allowed to cover the entire area between the injection and production wells. In order to inject a fluid into formations of low or negligible permeability it is often required that the formation be fractured. If fracturing is required the solvent is injected into the formation along the fracture. Whether introduced with the aid of fracturing or with normal injection only, the solvent is allowed to imbibe into the tar sand deposit. This may involve slow injection or injection followed by cessation of injection for a time to allow sufficient imbibition to take place. The imbibition of solvent is followed by injection of water over the same area as covered by the solvent. The water is then allowed to imbibe into the solvent soaked tar sand deposit. After the desired amount of imbibition has taken place, water is injected into the injection well and the bitumen, solvent and water are produced at the production well.

Many other variations of practicing my invention may be thought of by those skilled in the art without departing from the scope and spirit of my invention. The enumeration of the above typical embodiments is in no way intended to limit the scope of my invention.

Any liquid of low viscosity that is miscible in the tar sand oil without precipitating constitutents in the oil can be used as the solvent. Preferred solvents because of their relatively low cost and good solvent properties are aromatic hydrocarbons or mixtures of hydrocarbons containing substantial amounts of aromatic hydrocarbons. Examples of such hydrocarbons are benzene, toluene, xylene, and highly aromatic mixtures of hydrocarbons having a boiling point range substantially the same as gasoline. Kerosene can also be used. Highly paraffinic hydrocarbons such as LPG, light naphthas or condensate are usually not suitable because of their inability to dissolve asphaltic constituents of the tar sand oil.

Any aqueous fluid which is compatible with the formation is suitable for use in the method of my invention. The aqueous fluid may contain natural or artificial additives. For example, brine will naturally contain many inorganic impurities. Additives may be introduced into the aqueous fluid to improve the surface active properties of the aqueous fluid so that it can more effectively remove the petroleum from the formation surfaces. The surface active improving additives comprises the broad class of compounds known as surfactants. The useful surfactants must either disperse, solubilize, wet or emulsify the tars and oil. Many surfactants which are acceptable for use in my inventionare known in the art. They include, for example, anionics, such as, alkylbenzene-sulfonates, petroleum sulfonates, sulfosu'ccinates, naphthalene sulfonates, N-acyl-N- alkyltaurates, B-sulfoesters of fatty acids, a-olefln sulfonates and nonionics, such as, ethoxylated alkyl phenols, ethoxylated aliphatic alcohols, carboxylic esters, carboxylic amides, polyoxyalkylene oxide block copolymers. Certain cationic surfactants may also be used.

Other additives are also useful in the aqueous fluids of my invention either alone or in combination with the surfactants above. These include aqueous solutions of a base or a base and an amine solubilizing agent. The base or alkaline agent may be, for example, an alkali metal hydroxide, an alkaline earth metal hydroxide, or a basic salt of the alkali or alkaline earth metal which is capable of hydrolizing in an aqueous medium to give an alkaline solution. The amine solubilizing agent may be, for example, pyridine, quinoline, their derivatives. and mixtures thereof.

The beneficiating results of the aqueous carrier containing an alkaline agent and a solubilizing agent are believed to derive from the wettability improving characteristics of the alkaline agent and the solubilizing action of the solubilizing agent. The solubilizing agent is effective in releasing the tar sand oil from the sand surfaces and the alkaline agent improves the wettability of the sand surface.

The figure depicts a typical embodiment of my invention during a recovery operation. FIG. 1A shows an injection well and a production well 11 penetrating a tar sand deposit 12'. First solvent and then an aqueous fluid are injected via the injection well at perforations 13 into the tar sand deposit and each is allowed to imbibe in turn in area 14 of the tar sand deposit. FIG. 1B shows water 15 being injected into perforations 13 of the injection well after imbibition of the solvent and aqueous fluid has taken place and forming a front 16 to drive the bitumen, solvent and aqueous fluid already in the tar sand deposit in area 14 to the production well 11 where the fluids are produced through perforation l7.

EXPERIMENTAL EXAMPLE 1 Several cores of tar sands were covered with benzene and allowed to stand over night to imbibe the benzene. Much of the bitumen was dissolved in the benzene and much of the benzene was imbibed into the cores. The benzene saturated cores were then placed under water. Water was imbibed into the cores as could be seen by the large amount of hydrocarbons liberated from the cores. These visual observations prove that relatively large amounts of bitumen may be recovered by sequential solvent and water imbibition according to my invention.

EXAMPLE 2 A tar sand core similar to that used in Example 1 was immersed in water and allowed to stand over night. No hydrocarbons were liberated from the core during this time.

The above examples demonstrate the effectiveness of the process of my invention. Using imbibition techniques as described above a small amount of solvent may be used to liberate a large amount of tar sand oil which may then be more completely removed by an aqueous medium.

The scope of my invention is embodied in the appended claims and represents the only limitations of my invention.

I claim:

1. A method for extracting bitumen in situ from tar sand deposits comprising contacting the tar sand with a solvent capable of dissolving the bitumen,

allowing the solvent to remain in contact with the tar sand and imbibe into the tar sand deposit, cofrlltacting said tar sand subsequenty with an aqueous uid, allowing the aqueous fluid to remain in contact with the tar sand and imbibe into the tar sand deposit, and

producing the bitumen, aqueous fluid, and solvent mixture by conventional means.

2. A method as in claim 1 wherein the operations take place below the surface of the earth and wherein the solvent and aqueous fluid are introduced to the tar sand deposit through a well or wells penetrating the tar sand deposit.

3. A method as in claim I wherein the solvent is a hydrocarbon containing substantial amounts of aromatic- 4. A method as in claim 3 wherein the solvent is selected from the group consisting of benzene, toluene and xylene.

5. A method as in claim 4 wherein the solvent is benzene.

6. A method as in claim 1 wherein the aqueous fluid contains a surfactant.

7. A method as in claim 1 wherein the aqueous fluid contains a base and an amine solubilizing agent.

8. A method for extracting bitumen in situ from tar sand deposits comprising soaking the tar sand deposit in solvent to allow imbibition of the solvent into the tar sand deposit, soaking the solvent soaked tar sand deposit in an aqueous fluid to allow imbibition of the water into the tar sand, and producing the bitumen, aqueous fluid, and solvent mixture by conventional means. 9. A method as in claim 8 wherein the solvent is selected from the group consisting of benzene, toluene and xylene and the aqueous fluid contains a surfactant.

an amine solubilizing agent. 

2. A method as in claim 1 wherein the operations take place below the surface of the earth and wherein the solvent and aqueous fluid are introduced to the tar sand deposit through a well or wells penetrating the tar sand deposit.
 3. A method as in claim 1 wherein the solvent is a hydrocarbon containing substantial amounts of aromaticity.
 4. A method as in claim 3 wherein the solvent is selected from the group consisting of benzene, toluene and xylene.
 5. A method as in claim 4 wherein the solvent is benzene.
 6. A method as in claim 1 wherein the aqueous fluid contains a surfactant.
 7. A method as in claim 1 wherein the aqueous fluid contains a base and an amine solubilizing agent.
 8. A method for extracting bitumen in situ from tar sand deposits comprising soaking the tar sand deposit in solvent to allow imbibition of the solvent into the tar sand deposit, soaking the solvent soaked tar sand deposit in an aqueous fluid to allow imbibition of the water into the tar sand, and producing the bitumen, aqueous fluid, and solvent mixture by conventional means.
 9. A method as in claim 8 wherein the solvent is selected from the group consisting of benzene, toluene and xylene and the aqueous fluid contains a surfactant.
 10. A method as in claim 8 wherein the solvent is selected from the group consisting of benzene, toluene and xylene and the aqueous fluid contains a base and an amine solubilizing agent. 